The UK's most complete GLP-1 guide
Every Question Answered. Every Side Effect Explained.
- How GLP-1 medications work
- Mounjaro vs Wegovy compared
- Injection instructions
- Side effects & solutions
- What to eat on treatment
- FAQs answered
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How Much Does Mounjaro Increase By Compared to Wegovy?
Both Mounjaro (tirzepatide) and Wegovy (semaglutide) are prescription-only weight management injections available in the UK, but they increase by different amounts and follow different titration schedules. Mounjaro starts at 2.5 mg and increases by 2.5 mg increments up to a maximum of 15 mg weekly, whilst Wegovy starts at 0.25 mg and increases in smaller steps, reaching a maximum of 2.4 mg weekly. Understanding how these dose increases work helps explain why clinical trial results differ between the two medications and why your prescriber may recommend one over the other following a clinical assessment.
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Enter your height and weight below. Supports both imperial (stone & lbs) and metric (kg). Results include NHS category, healthy weight range, and ethnicity adjustments.
What Is BMI and Why Does It Matter?
Body Mass Index (BMI) is the most widely used screening tool for assessing whether your weight falls within a healthy range. Used by the NHS, GPs, and weight management services across the UK, BMI provides a quick snapshot of your weight relative to your height. The formula is simple: your weight in kilograms divided by your height in metres squared (kg/m²).
While BMI isn't a perfect measure — it doesn't account for muscle mass, bone density, or fat distribution — it remains the standard first step in identifying potential weight-related health risks including type 2 diabetes, cardiovascular disease, high blood pressure, and certain cancers.
The NHS also recommends adjusted thresholds for people of South Asian, Chinese, or Black African heritage — a BMI of 23 or above is classified as overweight, and 27.5 as obese. Our calculator includes this adjustment as a one-click toggle.
Dose Titration Schedules and Clinical Trial Comparisons
Mounjaro (tirzepatide) is a dual GIP and GLP-1 receptor agonist with a distinct dosing schedule. You start on 2.5 mg once weekly, with increases of 2.5 mg every 4 weeks if tolerated, moving through 5 mg, 7.5 mg, 10 mg, 12.5 mg, and finally 15 mg as the maximum maintenance dose. In the SURMOUNT-1 clinical trial, participants on 15 mg Mounjaro achieved average weight loss of approximately 20.9% of body weight over 72 weeks alongside a reduced-calorie diet and increased physical activity.
Wegovy (semaglutide) is a GLP-1-only agonist with smaller dose increments. It begins at 0.25 mg weekly, increasing by 0.25 mg steps through 0.5 mg, 1 mg, 1.7 mg, and reaching 2.4 mg as the maximum dose. Each dose is maintained for approximately 4 weeks before escalation. In the STEP-1 trial, participants on 2.4 mg Wegovy achieved average weight loss of approximately 14.9% of body weight over 68 weeks with the same lifestyle modifications.
The difference in dose increments reflects their different mechanisms. Mounjaro's dual action requires larger starting and escalation doses, whilst Wegovy's single GLP-1 mechanism uses smaller, more gradual increases. Both require a valid UK prescription following clinical assessment.
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How It Works
Three simple steps to understand your weight and take action.
Enter your height and weight in our free calculator. Get your BMI, NHS category, healthy weight range, and ethnicity-adjusted thresholds instantly.
If your BMI suggests you're overweight or obese, explore our GLP-1 calculators to project potential weight loss on Mounjaro or Wegovy.
Use our progress tracker to log your weight weekly, visualise your journey with charts, and stay motivated — all stored privately in your browser.
Free Weight Loss Tools & Guides
Everything you need to understand your weight, explore medication options, and track your progress — completely free.
Which Medication's Dose Schedule Suits You?
Your GP or licensed prescriber will consider your individual health, tolerance to side effects, and any existing medical conditions when choosing between Mounjaro and Wegovy. Neither medication is superior — they work differently, and response is highly individual. Some people tolerate larger dose increments better; others prefer a slower titration schedule. Both medications cause temporary side effects like nausea during dose escalation, which typically improve within days to weeks. Once you reach your target maintenance dose, you'll continue the same dose weekly for ongoing weight management. Calculate your current BMI and explore our GLP-1 weight loss calculator to understand your potential treatment pathway — your prescriber will always assess suitability based on your personal circumstances, not automated calculations.
- Dual GIP/GLP-1 receptor agonist
- Up to 22.5% body weight loss (SURMOUNT-1)
- Weekly injection, dose escalation over 20+ weeks
- Available via private prescription in the UK
- Doses: 2.5mg → 5mg → 7.5mg → 10mg → 12.5mg → 15mg
- GLP-1 receptor agonist
- Up to 15–17% body weight loss (STEP trials)
- Weekly injection, 5-step dose escalation
- NHS & private prescription available
- Doses: 0.25mg → 0.5mg → 1mg → 1.7mg → 2.4mg
Mounjaro vs Wegovy: Head-to-Head
A side-by-side comparison of the two most popular GLP-1 weight loss medications available in the UK.
| Feature | Mounjaro | Wegovy |
|---|---|---|
| Drug class | Dual GIP/GLP-1 agonist | GLP-1 agonist |
| Active ingredient | Tirzepatide | Semaglutide |
| Avg. weight loss | 15–22.5% | 12–17% |
| Key trial | SURMOUNT-1 (2022) | STEP 1 (2021) |
| Max dose | 15 mg weekly | 2.4 mg weekly |
| Escalation period | 20–32 weeks | 16–20 weeks |
| Administration | Weekly injection (pen) | Weekly injection (pen) |
| NHS availability | Private prescription only | NHS & private |
| Approx. private cost | £150–£250/month | £150–£300/month |
| Common side effects | Nausea, diarrhoea, constipation | Nausea, vomiting, diarrhoea |
Data sourced from SURMOUNT-1 and STEP 1 clinical trials. Costs are approximate and vary by provider. Always consult a prescriber.
Am I Eligible for Weight Loss Medication?
In the UK, eligibility for GLP-1 weight loss medications like Mounjaro and Wegovy is based on your BMI and overall health profile.
- BMI of 30 or above (obese)
- Age 18 or over
- No contraindicated conditions
- Committed to lifestyle changes
- BMI of 27 or above
- Plus type 2 diabetes
- Or high blood pressure
- Or obstructive sleep apnoea
Use our BMI calculator to check whether your BMI falls within the eligible range.
How We Built These Tools
Every calculator and guide on myweightcheck is built with accuracy and transparency in mind. Our BMI calculator uses the standard WHO formula with NHS-aligned category thresholds. Our GLP-1 projections are modelled on published clinical trial data from SURMOUNT and STEP studies.
All data stays on your device. We don't require sign-ups, and we don't store your health information on any server. Your progress tracker saves data locally in your browser using localStorage, so only you can see it.
We're based in the UK and our tools are designed specifically for UK users — supporting stone & lbs by default, referencing NHS guidelines, using NICE-approved medication data, and linking to GPhC-registered pharmacies.
Frequently Asked Questions
Common questions about BMI, weight loss medications, and our free UK tools.
Does Mounjaro increase faster than Wegovy?
Mounjaro increases by larger absolute amounts (2.5 mg increments vs Wegovy's 0.25 mg steps), but both follow 4-week intervals between dose increases. Mounjaro reaches its maximum dose of 15 mg within approximately 20–24 weeks, whilst Wegovy reaches 2.4 mg in roughly 17 weeks. Both are gradual, medically supervised escalations.
Why is Mounjaro's maximum dose so much higher than Wegovy's?
The doses are not directly comparable — they're measured in the same units but represent different mechanisms. Mounjaro is a dual GIP+GLP-1 agonist, whilst Wegovy is GLP-1-only. The higher Mounjaro dose reflects its dual action. Clinical trial results show comparable weight loss percentages despite different maximum doses.
Can I switch from Wegovy to Mounjaro mid-treatment?
Yes, but only under prescriber guidance. There is no official conversion chart, though approximate equivalences exist (e.g., Wegovy 2.4 mg roughly approximates Mounjaro 10–15 mg in effect). Any switch requires medical review to determine the appropriate starting dose and titration schedule for your situation.
Which kwikpen dose schedule has fewer side effects?
Both medications cause similar side effect profiles — nausea, diarrhoea, constipation, and abdominal discomfort. These are common during dose escalation and typically improve within days. Starting at the lowest dose and increasing gradually helps minimise early side effects. Your prescriber will monitor your tolerance throughout titration.
What if I can't tolerate the dose increases for either medication?
Your prescriber can slow the titration schedule, delay an increase, or maintain a lower dose if tolerated well. There's flexibility within NHS NICE guidance and private prescribing practice. Some people benefit from staying on a lower dose long-term rather than pushing to the maximum — your GP will advise based on your response and health goals.
Ready to take control of your weight loss journey?
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